In optical communications networks, optical transmitter modules, optical receiver modules, and optical transceiver modules are used to transmit and receive optical signals over optical fibers. In a transmit portion of such an optical module, a laser generates modulated optical signals that represent data, which are then transmitted over an optical fiber. The laser can be, for example, a Vertical Cavity Surface Emitting Laser (VCSEL) or an edge-emitting laser. In a receive portion of such a module, an optics system directs light propagating out of the end of an optical fiber onto an optical detector or photodetector, which converts the optical energy into electrical energy. An photodetector is typically a semiconductor photodiode device, such as a PIN (p-type/intrinsic/n-type) photodiode. Optical transceiver modules typically include multiple lasers for transmitting multiple data signals and multiple photodiodes for receiving multiple data signals.
An optical module is commonly assembled by mounting the optical device, i.e., laser or optical detector, on a substrate, also referred to as a leadframe. As the optical device typically comprises a microelectronic semiconductor die, electrical connections between the die and conductors on the substrate are made by a technique known as wirebonding. Wirebonding is a technique in which one end of a very fine wire is bonded to a pad on the die using thermal or ultrasonic energy, and the other end is bonded to one of the conductors on the substrate. A lens assembly can be aligned with the transmit or receive optical ports of the die and mounted in fixed relation to the die and substrate.
Wirebonds are extremely fragile because the wires are extremely fine, i.e., thin gauge. Rough handling of the optical assembly can easily break or dislodge a wirebond. In some optical assemblies, the wirebonds are protected by an enclosure or module body that encloses the entire optical assembly. In some assemblies, the wirebonds are encapsulated in a dielectric resin to protect them.